Could very well be from overspray or drift from the gypsy moth spraying. Japanese maple foliage is very sensitive to just about anything other than pure water being sprayed on the foliage. A phytotoxic reaction occurs and bleaching, spotting or damage similar to what yours is showing is common. It's pretty much a rule of thumb NOT to spray a leafed-out JM for insect or disease issues.

With just that small amount of damage, it is more cosmetic than harmful to the tree. The leaves may or may not die and fall off.....if they do, new ones should form in their place.

Thanks for the response - I hope you're right, I don't want to lose the tree. The point of the second picture was to show that the center of the tree was less affected than the top canopy. Pretty much every outer branch is damaged.

A recent hot and or very bright day? If so, could be environmental.

Don't know what they spray for gypsy moth where you live &/or how it might affect your tree.

To obtain facts rather than speculation, call the agricultural authority and to ask about the possible effects from such sprays on a Japanese maple. Perhaps the remedy is to wash off any potential residue as soon after the spray as possible.

Good suggestions - next year I will definitely wash off the leaves after they spray (assuming they do).

I'm not sure how much 'speculation' is involved. Those leaves show classic symptoms of phytotoxicity. Japanese maples are extremely reactive to any oil based sprays, insecticidal soap and many common insecticides. Most JM sources clearly indicate to avoid contact with these types of products and even to avoid dormant season oil products.

Washing or rinsing the foliage will only be helpful or effective if it is done immediately after contact with the spray. Avoidance - if at all possible - is best. But it is very likely that damage that results in nearly complete defoliation will not be fatal - Japanese maples have the ability to releaf relatively easily if otherwise healthy plants.